Sustainable road surfaces with a high percentage of recycled materials

Company: TRADECOWALL (Société Coopérative pour le TRAitement des DÉchets de COnstruction en WALLonie), the Walloon cooperative union for the treatment of construction waste, aims to manage the deconstruction/construction waste generated by building sites in a circular and sustainable manner.
To achieve its objectives in a local and sustainable way, TRADECOWALL is developing a network of operating sites in Wallonia in partnership with numerous public and private entities.

Problem statement: In Wallonia, more than 6 million tonnes of mixed recycled aggregates (from the crushing of mixed inert waste: concrete, bricks, stones, ceramics, etc.) are produced annually from construction and demolition waste. These aggregates constitute an important deposit which is currently not sufficiently valorised.
From April 2018 to March 2020, TRADECOWALL and the Belgian Road Research Centre (BRRC) collaborated on the RIDIAS-project (Revêtement Innovant et Durable Incluant des Agrégats en Seconde Vie). The objective of this project was to demonstrate the technical feasibility of integrating high percentages of mixed recycled aggregates in the composition of base layers and concrete pavements for reallocation roads.

Action of the accredited research centre: Within the framework of this project, various innovative road structures were deployed on a 500-metre trial area (the chemin du Ridias in Gembloux). This section was divided into 10 sections of 50 metres in length, on which two types of base material and five concrete compositions were laid. The compositions of the materials were optimised in the BRRC laboratories, in order to maximise the substitution rate of natural aggregates by mixed recycled aggregates produced by TRADECOWALL, while ensuring that the road’s performance in terms of strength and durability was maintained.
On the northern part of the road, which is frequently flooded, a draining base layer consisting of 60 % mixed recycled aggregates and 40 % limestone aggregates was laid. In the southern part, the base layer is made of cement-bound mixed recycled aggregates.
Of the recycled pavements tested, two are conventional concrete pavement compositions, with substitution rates of 25 and 50 %, and two are dry roller-compacted concrete compositions, which are less expensive to install and allow aggregate substitution rates of up to 90 %.
Despite these high substitution rates, the laying of the new materials did not pose any specific technical difficulties. Long-term monitoring of the section is still underway to confirm the durability of the proposed solutions in the presence of climatic stresses and agricultural traffic.

Industrial benefits: The Ridias pilot project has enabled the laying of different mixtures of materials for road applications containing mixed recycled aggregates, going far beyond what is currently allowed in standards and standard tender specifications. The use of recycled materials in this way reduces the cost of road construction for the collectivity, while at the same time reducing its environmental impact.
BRRC and TRADECOWALL are thus paving the way for more circularity in road construction.

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